Plant fibers form a source for economically important products such as paper, cordage (cords and ropes) and textiles. A fiber is botanically defined as a long narrow tapering cell, dead and hollow at maturity with a rigid thick cell wall composed mostly of cellulose and usually lignin. Soft or bast fibers are found in the phloem (inner bark) of dicotyledonous stems (flax, jute, hemp, ramie). Hard or leaf fibers are found in monocot leaf vascular bundles (sisal, manilla hemp, pineapple). Surface fibers grown from the surface of seeds (cotton), leaves or fruits (coconut coir).
Cotton provides much of the high quality fiber for the textile industry and major efforts have been invested in obtaining cotton fibers with characteristics which suit the requirements of the industry through breeding by either classical methods or by genetically altering the genome of cotton plants.
Cotton fiber originates as a seed trichome, more specifically a single cell that initiates from the epidermis of the outer integument of the ovules, at or just prior to anthesis. The morphological development of cotton fibers has been well documented (Basra and Malik, 1984, Int Rev of Cytology 89: 65-113; Graves and Stewart, 1988, supra; Ramsey and Berlin, 1976, American Journal of Botany 63 (6): 868-876; Ruan and Chourey, 1998, Plant Physiology 118: 399-406; Ruan et al. 2000, Aust. J. Plant Physiol. 27:795-800; Stewart, 1975, Am. J. Bot. 62, 723-730). Cotton fibers, in particular from Gossypium hirsutum, undergo four overlapping developmental stages: fiber cell initiation, elongation, secondary cell wall biosynthesis, and maturation. Fiber cell initiation is a rapid process. White fuzzy fibers begin to develop immediately after anthesis and continue up to about 3 days post-anthesis (DPA), which is followed by fiber cell elongation (until about 10 to about 17 DPA). Depending upon growth conditions, secondary cell wall biosynthesis initiates and continues to about 25 to about 40 DPA, followed by a maturation process until about 45 to about 60 DPA. The secondary cell wall synthesis and maturation phase are commonly considered the “fiber strength building phase”. Only about 25 to 30% of the epidermal cells differentiate into the commercially important lint fibers (Kim and Triplett, 2001). The majority of cells does not differentiate into fibers or develop into short fibers or fuzz. During fiber elongation and secondary wall metabolism, the fiber cells elongate rapidly, synthesize secondary wall components, and show dramatic cellular, molecular and physiological changes. Fiber elongation is coupled with rapid cell growth and expansion (Seagull, 1991. In Biosynthesis and biodegradation of cellulose (Haigler, C. H. & Weimer, P. J., eds) pp. 1432163, MarcelDekker, New York) and constant synthesis of a large amount of cell metabolites and cell wall components such as cellulose. About 95% of the dry-weight in mature cotton fibers is cellulose (Pfluger and Zambryski, 2001, Curr Biol 11: R436-R439; Ruan et al., 2001, Plant Cell 13: 47-63). Non-celluloid components are also important to fiber cell development (Hayashi and Delmer, 1988, Carbohydr. Res. 181: 273-277; Huwyler et al., 1979, Planta 146: 635-642; Meinert and Delmer, 1977, Plant Physiol 59: 1088-1097; Peng et al., 2002, Science 295: 147-150). Compared to other plant cells, cotton fibers do not contain lignin in secondary walls but have large vacuoles that are presumably related to rapid cell growth and expansion (Basra and Malik, 1984, supra; Kim and Triplett, 2001, Plant Physiology 127: 1361-1366; Mauney, 1984, supra; Ruan and Chourey, 1998, supra; Ruan et al., 2000, supra; Van't Hof, 1999, American Journal of Botany 86: 776-779).
Developing cotton fiber cells are living cells and accordingly contain biological macromolecules such as peptides, proteins, and nucleic acids such as DNA and RNA. In contrast, mature fibers are dead, hollow cells, consisting mainly of cellulose. It is generally accepted that fiber cells, particularly cotton fiber cells, no longer contain extractable nucleic acids or proteins. Based on this inertness, cotton swabs are used as an applicator for medical substances as well as to take DNA samples from, most commonly, the inner cheek in forensic investigations.
In addition, plant fibers are subject to extensive processing prior to their use in industry, particularly prior to their use in the textile industry. In the case of cotton, processing from raw fiber in the field to finished apparel for sale involves numerous steps that vary greatly depending on the end product desired. The various possible steps in these processes can be divided generally into mechanical and chemical steps.
The process of harvesting and ginning cotton can subject the fiber to thermal and mechanical damage. No chemicals are applied during the ginning process. Heat is often utilized to dry cotton during the ginning process if it contains more than 8% moisture. Heat is usually closely regulated to avoid fiber damage. Mechanical damage can occur during the picking and ginning operations. This mechanical damage should affect a very low % of the total fibers.
During spinning, the process steps are primarily mechanical. Short fibers (immature and/or mechanically damaged fibers and foreign material are removed in the spinning process). The first chemical treatments in processing are made toward the end of the spinning process when yarn for knitting is treated with a lubricant and about half the yarn for weaving is treated with sizing material. Cotton yarn for knitting is most often treated with wax as a lubricant to facilitate movement of the yarn through the knitting equipment. Synthetic lubricants are also available but it is believed wax is still the most common treatment. Sizing, also called slashing, is applied to the yarn for weaving that will be used as the lengthwise strands in the finished fabric (the warp). The lateral (fill) yarn is not treated with sizing. The common material used for sizing is starch. Polyvinyl alcohol is also used for sizing and blends of starch and polyvinyl alcohol are common. Additives such as binders, humectants, softeners, wetting agents, defoamers and other adjuvants may be added to the sizing treatment.
Knitting and weaving are both mechanical processes involving no chemical or heat applications. At the end of the knitting and weaving processes, steps to prepare the resulting fabric for finishing involve the application of chemicals and in some cases, high temperatures. The preparation process objective of the finishing step is to remove impurities that will interfere with processing through dyeing, printing or other finishing steps. Primarily, the wax must be removed from knitted fabric (scouring) and the sizing must be removed from woven fabric (desizing). Other impurities that may be removed at this step include, seed husks, pectins and other chemicals. Chemicals used for desizing include enzymes to remove starch and soda, ash or detergents to remove polyvinyl alcohol. Scouring is done with organic solvents that will dissolve the wax or other lubricants used. After scouring or desizing, fabric is usually bleached using chlorine or peroxide bleach. Goals of bleaching are to remove any remaining non-fibrous material, hydrolysis, oxidation and removal of residual sizeing and improve absorbancy of dye. Bleaching with peroxide may involve steam or water bath at near boiling water temperatures and the bleach bath may contain additives such as stabilizers and sequestering agents. Bleaching with chlorine is done at lower temperatures (40 to 50 degrees Centegrade) and cellulose degradation is less than with peroxide. If chlorine is used for bleaching, an antichlor treatment is also required. Singeing with a controlled flame is carried out on some fabrics to clean the fabric surface and remove or reduce pilling. Optical brighteners may be added to fabrics or garments to be sold as white un-dyed products. Anionic organic optical brighteners are typically used on cotton. Several compounds are available and some can be added during bleaching.
Mercerization is a process that can be applied to cotton yarn or fabric to improve absorption of or reaction to dye and other chemical finishing treatments, improve breaking strength, improve dimensional stability, improve fabric smoothness and luster and cover immature cotton fibers. It is a process that involves treatment with NaOH, washing, acid scouring, rinsing and drying.
The most common finishing treatment is dyeing. It can be done at the yarn, fabric or garment stage. Dyes used for cotton are numerous and of many different types. The most common dye product for cotton is indigo but it represents only 4% of dyed fabric. Dyeing can be done as a continuous process or batch process. While the chemicals used for dyeing are numerous, the process customarily involves the use of high temperature, near boiling, in the dye vat to which the fabric, yarn or garments may be submersed for extended time. Printing is the other major process for adding color or design to textiles. Printing involves mostly a mechanical process for applying coloring inks to the surface of fabric or garments. Both dyeing and printing may involve the application of chemical fixing agents at the end of the process.
Another common finishing treatment, especially after dyeing is aggressive laundering. This would include use of detergents and other cleaning agents to remove residual finishing materials from the finished fabric or garment.
Many other mechanical and chemical finishing steps may be applied to fabric, yarn or garments involving numerous options of chemicals and treatment processes. Softeners alone may be of three different types and each type may involve several different chemicals.
Although the above overview of converting raw cotton fiber into end use textile products is highly generalized, it will be clear that a person skilled in the art would not expect to be able to extract peptides, proteins or nucleic acids from yarns, textiles or finished apparel products after the numerous chemical and thermal treatment steps customarily involved.
There is a need in the industry to be able to track the source and/or origin of plant fibers, particularly of mature and/or processed plant fibers. Such source and/or origin identification of plant fibers may be important for certification processes, guaranteeing production and processing of fibers of specified quality produced from specific germplasm, such as the FiberMax® Certification Program (www.certifiedfibermax.com). The capacity to track source and/or origin in mature and/or processed fibers also allows identification of plant fibers which have special characteristics, such as the fibers with improved chemical reactivity or dyeability as described in WO2006/136351.
Existing certification programs are based on recordation by growers or seed retailers of purchase of seeds of specific germplasm of a fiber crop, such as cotton, and identification of the produced fibers of the registered growers (in the case of cotton by permanent USDA bale identification numbers).
The ability to track source and/or origin of plant fibers, particularly of mature and/or processed fibers would be greatly improved if it would be possible to extract biological macromolecules from mature and or processed plant fibers which contain biological information related to the source plant of the fibers, such as peptides, proteins, nucleic acids, DNA or RNA. In this way, auditing of existing certification programs would be made possible. Additionally it would become possible to identify fibers at a later stage in the supply chain, beyond the growers or suppliers of fibers, such as e.g. at spinner, weaver or retail customer level.
Agricultural Research Service, USDA and Applied DNA Sciences worked together to develop a tagging system based on DNA embedded technologies to trace US-sourced cotton and textile components.
(on the worldwide web at seedquest.com/News/releases/2004/February/7829.htm).
It would thus be advantageous to be able to extract naturally occurring biological macromolecules from plant fibers, such as cotton fibers, particularly from mature and/or processed fibers, textiles, yarns or apparel, and further to be able to derive plant source related information from such plant fibers.
The methods described hereinafter in the different embodiments, examples, figures and claims provide a solution to the above mentioned problem, by allowing to extract natural biological macromolecules from plant fibers, such as cotton fibers, particularly from mature and/or processed fibers, textiles, yarns or apparel, and further to be able to derive plant source related information from such plant fibers.